This invention relates in general to fixtures for securing vehicle wheels upon machining stations during machining operations and in particular to a chuck with counterweights for securing a vehicle wheel upon a wheel lathe.
Light weight alloy vehicle wheels are becoming increasingly popular. Such wheels typically include an annular wheel rim that carries a tire. A circular wheel disc is formed across one end of the wheel rim. The wheel disc usually includes a central hub portion supported within the wheel rim by a plurality of wheel spokes. A central pilot hole and plurality of wheel mounting holes are formed through the wheel hub.
One conventional process for manufacturing light weight alloy wheels involves pouring molten metal into a wheel mold to form a casting of a one-piece wheel. After the molten metal solidifies, the wheel casting is removed from the mold. The wheel casting is oversized and is machined to a final shape. Alternately, a full face wheel disc that includes the outboard tire bead retaining flange is cast from a light weight alloy and machined to final shape. A partial wheel rim that can be rolled from a strip of steel is then welded to an inboard surface of the wheel disc to form a two piece wheel. Such a wheel combines the low cost and strength of a steel rim with a pleasing aesthetic appearance of a wheel disc cast from a light weight metal and is usually referred to as a bimetal wheel.
Machining the wheel or wheel disc casting typically includes multiple operations. Sawing machines cut any casting gates and risers from the casting. A drilling machine is used to drill the wheel mounting holes through the wheel hub. The wheel casting is then mounted upon a wheel lathe for machining to its final shape. During the lathe operations, the inside surface of the wheel hub is usually faced to provide a flat mounting surface. Similarly, the outboard wheel hub surface is faced and both the inside and outside of the wheel rim are turned to their final shapes. The central pilot hole is usually drilled while the casting is clamped in the lathe for turning the inboard tire bead seat.
Referring now to the drawings, there is shown generally at 5 in FIGS. 1 and 2 a prior art wheel chuck. The known chuck 5 is suitable for clamping a wheel casting (not shown) or vehicle wheel 10 upon a wheel lathe (not shown). The chuck 10 includes a plurality of jaws 11. While three jaws 11 are shown in FIG. 1, the chuck 10 also may have four jaws. As best seen in FIG. 2, each jaw 11 includes a stepped portion 12 that includes a plurality of arcuate shaped clamping surfaces labeled 13, 13a and 13b, having different radii. The stepped portion 12 is carried upon the upper surface of a wedge shaped actuator plate 14 and is attached thereto by threaded fasteners 16. Alternately, the stepped portion 12 and the respective actuator plate 14 may be formed integrally as a one piece jaw (not shown). As best seen in FIG. 2, a guide rib 15 extends from the lower surface of each actuator plate 14 in a radial direction from the center of the chuck 10. As shown in FIG. 2A, the guide rib 15 is preferably formed having an inverted T cross sectional shape.
The actuator plates 14 are moveably mounted upon a support structure, indicated generally at 17. The support structure 17 includes a circular face plate 18 rotatably supported by bearings 20 upon a cylindrical riser 22. A plurality of radial slots 23 are formed in the upper surface of the face plate 18 with each of the slots having an inverted T cross sectional shape that mirrors the shape of the actuator plate guide ribs 15. Each radial slot 23 slidably receives a corresponding actuator plate guide rib 15 and cooperates with the rib to retain the actuator plate 14 upon the face plate 18 while guiding the actuator plate for movement in a radial direction. The face place 18 is drivingly coupled to a rotatable lathe spindle 24 that passes through a central aperture 26 formed through the riser 22.
Prior to mounting of the vehicle wheel 10a upon the chuck 10 for machining operations, at least one of the jaws 11 is moved in an outward radial direction, as generally indicated by the arrow labeled 28 in FIG. 1, to an open position. The movement is accomplished by urging the corresponding guide rib 15 outward within its respective face plate slot 23 by a conventional hydraulic ram or a mechanical mechanism (not shown). Typically, all of the jaws 11 are simultaneously moved outward. Once the jaws 11 are opened, the wheel 10a is placed upon an appropriate step, such as the step defined by the arcuate shaped clamping surface 13. The chuck 10 can accommodate wheels of different diameters, such as wheels 10a and 10b (shown in phantom in FIG. 2) that would be placed upon steps 13a and 13b, respectively. The jaws 11 are then moved in a radial inward direction to a closed position, as indicated by the arrow labeled 29, clamping the wheel 10a within the chuck 10.
During machining of the vehicle wheel 10, the lathe spindle 24 rotates the chuck 10 and the wheel 10, as indicated in FIG. 1 by an arrow labeled 30. The rotational motion generates centrifugal forces that urge the jaws 11 in a radial outward direction, as indicated by the arrow 28 in FIG. 1. If the centrifugal forces are sufficiently large, the jaws 11 will move in a radial outward direction and the chuck 10 will loosen upon the wheel 26 allowing the wheel to slip relative to the jaws 11. Thus, it would be desirable to provide a wheel chuck with jaws that would not be effected by centrifugal forces.